3,3-DI-(Substituted azaphenanthen-8-yl)phthalides and naphthalides

ABSTRACT

This invention relates to a class of phthalein indicator dyes useful as optical filter agents in photographic processes to protect a selectively exposed photosensitive material from further exposure during processing in the presence of indicident light. Such dyes comprise 3,3-disubstituted phthalides and 3,3disubstituted naphthalides wherein the 3,3 substituents are parahydroxy polycyclic aryl radicals possessing a nitrogen atom included in the ring system adjacent to the para-hydroxy group.

United States Patent [1 1 [111 3,920,667 Idelson [451 Nov. 18, 19753,3-Dl-(SUBSTITUTED [51] Int. Cl. C07D 215/14AZAPHENANTHEN-S-YL)PHTHALIDES [58] Field of Search 260/289 R, 283 S ANDNAPHTHALIDES Elbert M. Idelson, Newton Lower Falls, Mass.

Polaroid Corporation, Cambridge, Mass.

Filed: Sept. 17, 1973 Appl. No.: 398,195

Related US. Application Data Division of Ser. No. 177,513, Sept. 2,l971, Pat. No. 3,779,754.

Inventor:

Assignee:

Primary Examiner-Richard J. Gallagher Assistant Examiner-Mary C. VaughnAttorney, Agent, or Firm-Sybil A. Campbell [57] ABSTRACT This inventionrelates to a class of phthalein indicator dyes useful as optical filteragents in photographic processes to protect a selectively exposedphotosensitive material from further exposure during processing in thepresence of indicident light. Such dyes comprise 3,3-disubstitutedphthalides and 3,3-disubstituted naphthalides wherein the 3,3substituents are parahydroxy polycyclic aryl radicals possessing anitrogen atom included in the ring system adjacent to the parahydroxygroup.

4 Claims, No Drawings 3,3-DI-(SUBSTITUTED A'Z'AP I-IENANTHENS-YL)PIITI-IALIDES AND.

V NAPHTHALIDES CROSS REFERENCE TO RELATED I APPLICATIONS Thisapplication is a division or uis. application Ser. No. 177,51 3'filedSept} 2, 1971', now UfSIf'Pat. No. 3,779,754. V

BACKGROUND OF THE INVENTION 1'. Field of the Invention The presentinvention relates to nove'l chemical compounds,and m'ore specifically,it relates to a new class of'ph'thalein indicator dyesjIn a particularaspect it relates to certain phthaleins useful as optical filteragentsin photographic processes for protecting an exposed photosensitivematerial from post-exposure fogging during development in the presenceof extraneous incident light and to such photographicuses.

2. Description of the Prior Art A number of photograpic processes bywhich images may be developedand viewed within seconds or minutes afterexposure have been proposed. Such processes generally employ aprocessing composition which is suitably distributed between twosheet-like elements, the desired image being carried by one of saidsheet-like elements. The resulting images may be inblack-and-white,'e.g.,' insilver, or in oneor more colo'rs. Processingmaybe conducted in or outside of a camera. Them ost useful'of suchprocesses are the diffusion transfer processes which have been proposedfor forming silver or dye images, and several of these processes havebeen commercialized. Such processes have in common the feature that thefinal image is a function of the formation of an image-wise distributionof an image-providingreagent and the diffusion transfer of saiddistribution to or from the stratum carrying the final image, whetherpositive or negative.

U.S. Pat. No. 3,415,644 discloses a composite photosensitive structure,particularlyadapted for use in reflection type photographic diffusiontransfer color processes. This structure comprises a pluralityof'essential layers including, in sequence, a dimensionally stableopaque layer; one or more silver halide emulsion layers havingassociated therewith dye image-providing material which is soluble anddiffusible, in alkali, at a first pH, as a function of thepoint-to-point degree of its associated silver halide emulsions exposureto incident actinic radiation; a polymeric layer adapted to receivesolubilized dy'e image-providing material ,diffusing thereto; apolymeric layer containing sufficient acidifying capacity toeffectreduc'tion of a processing composition from thefirstpI-Ito asecond atwhich the dye image-providing material is substantiallynondiffusible; and a dimensionally stable transparent l ayer. Thisstructuremay be exposed tolincident actinic radiation and processed byinterpo'sing, intermediatethe silver halidee'mulsioh' layer and thereceptiorilayer, an alkaline processing composition providing thefirstpH and containing a light-reflecting agent, for example,-titaniumdioxide to provide a white'background. The light reflectingagent (referred to in said patent as an fopacifying agent) also performsan opacifying function, i-.e., it is effective to mask the developedsilver halide ernulsions and also acts to protect the photoexpbsed emu]sions from postexposure'fog gihg by light passing through thetransparent layer if the photo-exposed film unit "s removedfrom thecamera before-image formation is complete. H

In a preferred embodiment, the composite photosensitive structureincludes a rupturable container, retaining the alkaline processingcomposition having the first pH "and light reflecting agent, fixedlypositioned extending transverse .a leadingv edge of the compositestructure in order to effect, upon application of compressive pressureto the container, discharge of the processingcomposition intermediatethe opposed surfaces of. the reception layer and the next adjacentsilver halide emulsion.

The liquid processing composition distributed intermediatethe receptionlayer and the silver halide emulsion, permeates the silver halideemulsion layers of the composite photosensitive structure to initiatedevelopment of the latent images contained therein resultant fromphotoexposure. As a consequence of the developme nt of the latentimages, dye image-providing mate- .rial associated with each of therespective silverhalide emulsion layers is individually immobilized as afunction of. the point-to-point degree of the respective silverhalide.emuls ion layer photoexposure, resulting in imagewisedistributions-of mobile dye image-providing materials adapted totransfer, by.,diffusion, to the reception layer to provide the-desiredtransfer dye image. Subsequentto substantial dye image formation in thereception layer, a sufficient portionof the ions of the alkalineprocessing composition transfers, by diffusion, to the polymericneutralizing layer to effect reduction in the alkalinity of thecomposite film unit tothe second pH at which dye image-providingmaterial is substantially nondiffusible, and further dye image-providingmaterial transfer is thereby substantially obviated.

The trahsfer 'clye image is viewed, as a reflection image, throughthedimensionally stable transparent layer {against,the background providedby the reflecting N o,.3 ,6{17,437 in. part a continuation of Ser. No.

2 786,352, an organic light-absorbing reagent (or optical filter agent),such, as a dye, which is present as a lightabsorbing species at. thefirst pH and which may be converted to a substantiallynon-light-absorbing species at the second pH is used in conjunction withthe lightreflecting agent to protect theselectively exposed silverhalide emulsions from post-exposure fogging when development of thephotoexposed emulsions is conducted in thepresence of extraneousincident actinic radiation impingingon the transparent layer of the filmunit.

hydroxy-substituted carbocyclic aryl compounds, viz., particular phenolsand naphthols which due to their high pKa and spectral absorptioncharacteristics are useful as optical filter agents for absorbingincident radiation actinic to selectively exposed photosensitivematerials within a predetermined wavelength range in the longerwavelength region of the visible spectrum. Among the dyes disclosedtherein are phenol and lnaphthol phthaleins wherein the p-hydroxyphenylor p-hydroxynaphthyl radicals are substituted with a hydrogen-bondinggroup on a carbon atom adjacent to the functional hydroxy group to raisethe pKa. These phenol and l-naphthol phthaleins form the subject matterof copending US. patent application Ser. Nos. 103,864 and 103,865,respectively both filed Jan. 4, 1971, now US. Pat. Nos. 3,833,615 and3,833,614.

The association of two atoms through hydrogen to form a hydrogen bondbetween or within molecules is well known. When hydrogen is attached toan electronegative atom, for example, or N, the resultant bond ispolarized. If directed toward another atom (M) with an unshared pair ofelectrons, the hydrogen acts as a bridge between the atoms (OH M) due tothe electrostatic attraction to both atoms between which the hydrogenproton can be transferred. In the phenol and naphthol phthaleins of thetwo aforementioned applications, an intramolecular hydrogen bond isformed between the p-hydroxy group and the hydrogen-bonding groupsubstituted on an adjacent carbon atom.

The present invention is concerned with another class of phthaleinindicator dyes possessing a high pKa which dyes also are among thosedisclosed as optical filter agents in aforementioned U.S. applicationSer. No. 103,392.

SUMMARY OF THE INVENTION It is therefore the primary object of thepresent invention to provide a novel class of phthalein indicator dyes.

It is another object of the present invention to provide products,compositions and processes for the development of photosensitivematerials in which the novel phthalein indicator dyes are used.

Other objects of this invention will in part be obvious and will in partappear hereinafter.

The invention accordingly comprises the processes involving the severalsteps and the relation and order of one or more of such steps withrespect to each of the others, and the products and compositionspossessing the features, properties and the relation of elements whichare exemplified in the following detailed disclosure, and the scope ofthe application of which will be indicated in the claims.

According to the present invention, there is provided a novel class ofphthalein indicator dyes derived from certain hydroxy-substitutedpolycyclic aryl compounds having a nitrogen atom included in the ringsystem as exemplified by -hydroxy-4-azaphenanthrene. These dyes includeboth phthalides and naphthalides and will be defined with greaterparticularity hereinafter.

The indicator dyes of the present invention, like phthalein indicators,in general, possess spectral absorption characteristics which arereversibly alterable in response to changes in environmental pH. Thesedyes possess a highly colored form capable of absorbing visibleradiation in alkaline media at a first pH value above their respectivepKa and a substantially colorless form, i.e., a form which issubstantially non-light- 4 absorbing in the visible spectrum in lessalkaline media at a second pH value below their respective pKa. By pKais meant the pH at which about 50% of the dye is present in itslight-absorbing form and about 50% is present in its non-light-absorbingform.

It will be appreciated that such compounds will find utility intitrations and other analytical procedures where phthalein indicatordyes are commonly employed, for example, to measure changes in pH valueas reflected by the change in color of the dye from one color to anotheror from colored to colorless or vice versa. The indicator dyes of thepresent invention, however, compared to conventional phthaleins ofhydroxysubstituted compounds, such as, simple phenol phthalein andl-naphthol phthalein possess a higher pKa which render them useful asoptical filter agents in photographic processes performed under alkalineconditions, and especially in photographic processes employing highlyalkaline media.

For a fuller understanding of the nature and objects of the invention,reference should be had to the following detailed description.

DESCRIPTION OF THE PREFERRED EMBODIMENTS According to the presentinvention, it has been found that phthalein indicator dyes having a highpKa may be obtained without adding substituents i.e., without having tosubstitute hydrogen-bonding groups on the phydroxy radicals of the dye.This may be achieved by utilizing hydroxy-substituted polycyclic arylcompounds having a nitrogen atom included in the ring system, providedthe nitrogen atom is in a position to give a group,

OH N: or (Y I K As compared to phenol and l-naphthol compoundscontaining a cyclic substituent subject to rotation, such hydrogenbonding is particularly effective in the compounds of the presentinvention since the N atom of the polycyclic molecule is infixedposition relative to the functional hydroxy group. Besides the increasein pKa resulting from the hydrogen bond thus formed, these dyes arecapable of absorbing radiation over a relatively broad wavelength rangein the visible spectrum. Because of their spectral absorptioncharacteristics and because they are colored at a comparatively high pH,they are especially useful as optical filter agents in photographicprocesses conducted under highly alkaline conditions for affordingprotection of a selectively exposed photosensitive material fromincident actinic radiation in the visible spectrum.

The indicator dyes of the present invention may be defined as phthaleinsselected from 3,3-disubstituted phthalides and 3,3-disubstitutednaphthalides wherein the 3,3-substituents are polycyclic aryl radicalscon- 5 taining the group,

said radicals being bonded to the phthalide or naphthalide by a carbonatom para to the -OH of said group. Illustrative of the aforementionedgroups are wherein A and A comprise a ring, the atoms which arenecessary to complete said ring being saturated or unsaturated and saidring being carbocyclic or heterocyclic, and preferably, containing 5 or6 members; and B and B comprise a ring system containing at least 5members.

Typical of the indicator dyes of the present invention are thoserepresented by the formula:

wherein Y and Y, the same, represent the atoms necessary to complete aring having 5 or 6 members; 2 and Z, the same, represent the atomsnecessary to complete aring system having at least 5 members and Xrepresents the atoms necessary to complete a ring-closing moietyselected from a phthalide and a naphthalide.

The indicator dyes defined above and as represented in the foregoingformula may contain substituents on the polycyclic aryl radicals and/orring-closing moiety as may be desired which do not interfere with thefunction of the dye for its selected ultimate use. Where it is desiredthat the indicator dye be substantially immobile or non-diffusible inthe processing solution, it may be S substituted with a bulky group,such as, a long chain substituent, e.g., dodecyloxy, hexadecyl ordodecylphenyl. Also, it may be substituted with solubilizing groups,e.g., carboxy or sulfo to adjust the solubility in a given solution.Because of the convenience in preparation, the dyes of the presentinvention preferably are symmetrical, i.e., bis phthalides and bisnaphthalides wherein the two polycyclic aryl radicals are the same,i.e., they contain the same substituents in the same position.

Typical substituents include branched or straight chain alkyl, such as,methyl, ethyl, isopropyl, n-butyl, t-butyl, hexyl, octyl, dodecyl,hexadecyl, octadecyl and eicosanyl; aryl, such as, phenyl,2-hydroxyphenyl, and naphthyl; alkaryl, such as, benzyl, phenethyl,phenylhexyl, p-octylphenyl, p-dodecylphenyl; alkoxy, such as, methoxy,ethoxy, butoxy, l-ethoxy-Z-(B-ethoxyethoxy), dodecyloxy andoctadecyloxy; aryloxy, such as phenoxy, benzyloxy, naphthoxy;alkoxyalkyl, such as methoxyethyl, dodecyloxyethyl; halo such as,fluoro, bromo, and chloro; trifluoralkyl, such as, trifluoromethyl,monoand bis-trifluoromethyl carbinol; sulfonamido; sulfamoyl; acyl andits derivatives; aminomethyl; amido; sulfonyl; sulfo; cyano; nitro;amino including mono-and disubstituted-amino, e.g., N-ethyl amino andN,Ndimethylamino; carboxy; and hydroxyl.

Specific examples of indicator dyes within the scope of the presentinvention are as follows:

The indicator dyes of the present invention may be prepared in aconventional manner by reacting the selected hydroxy-substitutedpolycyclic aryl compound and the phthalic or naphthalic acid reagent atelevated temperatures in the presence of a suitable catalyst, such as, aLewis acid catalyst as conventionally used in Friedel Craft reactions,e.g., aluminum chloride, ferric chloride, stannic chloride, borontrifluoride and zinc chloride. Ordinarily, an inert organic solventcapable of dissolving the reactants also is employed, e.g.,nitrobenzene.

The phthalic or naphthalic acid reagent selected to ultimately form thering-closing moiety may be the acid, the acid anhydride or the acidchloride. The terms phthalic acid reagent and naphthalic acid reagent asused herein are intended to include the corresponding anhydrides andacid chlorides. These reagents may be substituted, with solubilizinggroups, such as, carboxy, e.g., hemimellitic acid; with long chainsubstituents to adjust the mobility of the final dye, e.g., sulfonamidocontaining a long chain alkyl group (-N- H-SO -nC l-I or with othersubstituents as may be desired.

Another method of preparing these phthalein indica- OH HN i tor dyescomprises reacting the selected hydroxy-substituted polycyclic arylcompound with phthalaldehydic or naphthalaldehydic acid, which acids maycontain substituents in the presence of a mild acid catalyst to yieldthe corresponding (na)phthalidyl-substituted intermediate which is thenoxidized by treating with dichlorodicyanoquinone or other suitableoxidizing agent. The oxidized intermediate is then reacted with anothermole of polycyclic aryl compound to yield the desired dye. This methodof preparing certain phthalein indicator dyes forms the subject matterof copending U.S. Pat. application Ser. No. 446,716 filed Feb. 28, 1974,a continuation-in-part of Ser. No. 108,662 filed Jan. 21, 1971.

As noted above, the hydroxy-substituted polycyclic aryl compounds usedas the starting materials in these methods contain the group,

It will be appreciated that the aryl compounds used as the startingmaterial may contain substituents as may be desired in the complete dye.provided the carbon atom para to the hydroxy group is unsubstituted andthus, available for reaction with the selected acid. If desired,substituents may be substituted on the completed dye, e.g., SO H groups.

The following Examples are given to further illustrate the presentinvention and are not intended to limit the scope thereof.

EXAMPLE 1 Preparation of the Compound of Formula (1) 19.5 grams of5-hydroxy-4-azaphenanthrene was dissolved in 60 ml. of nitromethane, ina flame dried, three-neck flask under dry (P nitrogen with stirring. Tothis light yellow solution was added 8 grams of fresh aluminum chloridein small portions. The solution turned more orange and someprecipitation took place. To this solution was added 2.105 grams ofhemimellitic anhydride acid chloride; the solution turneda reddishorange. 20 ml. of nitrobenzene was then added, and the solution washeated with stirring on an oil bath at 40C. After 6 hours, the solutionturned greenish in color. To this solution was added an additional 1.95grams of 5- hydroxy-4-azaphenantrene, the reaction was then heated at60C. with stirring for 1 hour. Anv emerald green color developed. Tothis solution, 0.72 ml. of acetic anhydride was slowly added, dropwise;the reaction was heated at 60C. with stirring for 48 hours. The reactionwas followed by T. L. C. [chloroform/methanol 1:1 on silica gel].Indicator was detectedzwith 5% sodium hydroxide in 20% aqueous ethanol.The reaction mixture was then poured into ice 100 g.) with stirring and100 ml. of 5% hydrochloric acid was added. The flask was washed withmethanol and the methanol combined with the water solution. The solutionwas then steam distilled for 4 hours to remove the methanol,nitromethane, and nitrobenzene. The aqueous solution was then filtered.The residue solid by T. L. C. was largely product 80% by weight).- Thefiltrate contained only a small amount of indicator. The solid wasdissolved in methylene chloride and evaporated onto silica gel. This wasthen eluted on a silica gel column with chloroform and aqueous methanolto yield the indicator dye. Some of the indicator became absorbed on thecolumn. This was soxlet extracted with chloroform for 24 hours. Totalyield of the title compound was 1.05 grams as a light yellow solid.

EXAMPLE 2 Preparation of the Compound of Formula (3) In a 100 ml.three-neck flask under nitrogen l g. of the product of Example 1 abovewas dissolved in small portions into 50 ml. of fuming sulfuric acid withstirring. The reaction solution turned a very dark emerald green. After2 hours of stirring at room temperature T. L. C. [methanol/chloroform onsilica gel] showed no starting material. The solution was then carefullypoured onto 200 g. of ice and the flask washed with 100 ml. of water.The aqueous solution was filtered to give a yellow solid which wasslurried with a small amount of methanol, filtered and dried to yield670 mg. of the title compound. An additional 200 mg. of productprecipitated from the aqueous solution overnight. Melting point 180C.(dec.).

The 5-hydroxy-4-azaphenanthrene used in Example 1 above was prepared inaccordance with the procedure described in Helv. Chem. Acta, vol. 27, p.1461 (1944).

As noted above, the indicator dyes of the present invention have arelatively high pKa as compared to conventional phthaleins ofhydroxy-substituted. compounds, such as, phenol and l-naphtholphthaleins. For example, the pKa values measured for the indicator dyesof Examples 1 and 2 were 13.8 and 13, respectively. In comparison,l-naphtholphthalein has two pKas, one at about 7 and a second at about8. Phenol phthalein and phenol 7-carboxy phthalein both have pKas ofabout 9.6. i

The pH sensitive indicator dyes of the present invention may be used asoptical filter agents in any photographic process including conventionaltray processing and diffusion transfer photographic techniques. In suchprocesses, the dye of dyes during development of a selectively exposedphotosensitive material will be in a position and in a concentrationeffective to absorb a given level of non-selective radiation incident onand actinic to the photosensitive material. The dyes may be initiallydisposed in the film unit, for example, in a layer(s) coextensive withone or both surfaces of the photosensitive layer. Where selectiveexposure'of the photosensitive material is made through a layercontaining the indicator dye, then the dyes should be in anon-light-absorbing form until the processing solution is.applied.Alternately, the dyes may be initially disposed in the processingcomposition in their lightabsorbing form, for example, in the developingbath in tray processing or in the layer of processing solutiondistributed between the photosensitive element and the superposedimage-receiving element (or spreader sheet) in diffusion transferprocessing. The particular indicator dye or dyes selected should have anabsorption spectrum corresponding to the sensitivity of thephotosensitive layer, so as to afford protection over the predeterminedwavelength range required by the particular photosensitive materialemployed and should have a pka such that they are in their colored form,i.e., light-absorbing form at the pH at which the photographic processis performed. Most commercially useful photographic processes areperformed under alkaline conditions. Diffusion transfer processes, forexample, usuallyemploy highly alkaline processing solutions having a pHin excess of 12.

In photographic processes where the optical filter agent is retained ina stratum through which the final image is to be viewed, the color ofthe indicator dye may be discharged subsequent to image formation byadjusting the pH of the system to a value at which the dye issubstantially non-light absorbing in the visible spectrum. Inphotographic processes performed at an alkaline pH, the optical filteragent, such as, a dye or dyes of the present invention are renderedsubstantially colorless by reducing the environmental pH. In processeswhere the optical filter agent is removed or separated from the layercontaining the final image or retained in a layer that does notinterfere with viewing of the final image, it is unnecessary to convertthe indicator dye to its non-light-absorbi'ng form, though the color maybe discharged if desired. i

The concentration of indicator dye is selected to provide the opticaltransmission density required/in combination with other layersintermediate the silver halide emulsion layer(s) and the incidentradiation, to prevent nonimagewise exposure, i.e., fogging, by incidentactinic light during the performance of the particular photographicprocess. It has been found, by interposing neutral density (carboncontaining) filters over a layer of titanium dioxide, that atransmission density of approximately 6.0 from said neutral densityfilters was effective to prevent fogging of a diffusion transfermulticolor film unit of the type described in said US. Pat. No.3,415,644 having a transparent support layer and an Equivalent ASAExposure Index of approximately 75, when processes for-1 minutein-l0,000 foot candles of color corrected light, a light intensityapproximating the intensity of a noon summer sun. The transmissiondensity required to protect such a film unit under the stated conditionsmay also be expressed in terms of the system transmission density of allthe layers intermediate the silver halide layer(s) and the incidentlight; the system.transmission density required to protect color filmunits of the aforementioned type andphotocess by following the abovedescribed procedure or obvious modifications thereof.

Since most commercial photographic processes e ploy photosensitivematerials sensitive to andexposable by.actinic:radiationthroughout thevisible;spectrum,e.g., black-and-white panchromatic silver halideemulsions and multilayer silver halide emulsion elements, it ispreferred to use a second dye(s) in conjunction with the subject dye(s)that has a principal absorption in a second and at least partiallydifferent predetermined wavelength range such that the combination ofdyes will afford protection from non-selective incident actinicradiation over the range of 400 to 700 nm. The

18 sion transfer photosensitive elements including a film pack or rollwherein superposed photosensitive and image-receiving elements aremaintained as a laminate after formation of the final image. Suchelements include at least one transparent support to allow viewing ofthe final image without destroying the structural integrity'of the filmunit. Preferably, the support carrying the photosensitive layefls)isopaque and the support carrying'the image-receiving layer istransparent and selective photoexp osur'e of the photosensitive layer(s)and viewing of the final image both are effected through thelattersupport. The final image is viewed as a reflection p'rint, i.e.,by reflected light, provided by a reflecting agent initially disposed inthe processing composition applied and maintained intermediate theimage-receiving and next adjacent photosensitive layer or by a preformedlayer of reflecting agentinitially positioned intermediate theimage-receiving and next adjacent photosensitive layer. It will beunderstood that a preformed reflecting layer, while it should be capableof maskingthephotosensitive layer(s) subsequent to imageformation,should not interfere with selective photo exposu re of thephotosensitive material prior to processing.

When utilising reflection-type composite film units, :he indicator dyeor dyes employed as the optical filter agent( s) may bepositionedinitially in a layer of the film unit, e.g., ina layer between theimage-receiving and. next adjacent photosensitive layer through whichphoto-exposure is effected provided it isincorporated under conditions,i .e., at a pH such'that it will not absorb actinic radiation intendedto selectively expose the photosensitive material to form a latent imagetherein. For example the optical filter agent maybe in a layercoatedovet' either the image-receiving layer or the next adjacentphotosensitive layer and should remain substantially non-light-absorbinguntil a processing combeing initially disposed in the film unit, theindicator second dye employed may be-non-color changing but toprocessing may be'removed from the film unit'or retained within the filmstructure, provided it is in a form or position such that itdoes' notinterfere with viewing of the image produced. t

The dyes of the present invention are especially useful as opticalfilter agents in diffusion transfer processes, for example, thoseemploying composite diffudyemaybe initially present in the processingcomposition appliedintermediate the image-receiving andnext adjacentphotosensitive'layer subsequent to photoexposure. The dye, wheninitially disposed in the processing composition, will be in itslight-absorbing form.

The dyes selected as optical filter agents should exhibit at the initialpH of the processing, maximumspectral absorption of radiation at thewavelengths to which the film units photosensitive silver halide layeror layers are sensitive, and preferably, should be substantiallyimmobile or non-diffusible in the alkaline processing composition inorder to achieve optimum efficiency as a radiation filter and to preventdiffusion of filter agent into layers of the film unit where itspresencemay be undesirable. Recognizing that the filter agent absorptionwill detract from image-viewing characteristics by contaminatingreflecting pigment background, the selected agents should be thoseexhibiting major spectral absorption at the pH at whichprocessing iseffected and minimal absorption at a pH below that which obtains duringtransfer image formation. Accordingly, the selected optical filter agentor agents should possess a pKa below that of the processing pH and abovethat of the environmental pH subsequent to transfer image formation.

As discussed previously, the concentration of indicator dye is selectedto provide the optical transmission density required, in combinationwith other layers intermediate the silver halide emulsion layer(s) andthe incident radiation, to prevent nonimagewise exposure, i.e., fogging,by incident actinic light during the performance of the particularphotographic graphic process. In the processes where the indicator dyeor dyes selected as optical filter agents are used in conjunction with areflecting agent or agents, the optical filter agents and reflectingagents together should possess the optical transmission densitynecessary to protect the photosensitive material for the particularphotographic process. The optimum concentration of optical filteragent(s) or filter agent(s) together with reflecting agent(s) may bereadily determined empirically for each photographic system.

While substantially any reflecting agent may be employed for the layerof reflecting agent, either preformedor applied as a component of theprocessing composition, it is preferred to select an agent that will notinterfere with the color integrity of the dye transfer image, as viewedby the observer, and, most preferably, an agent which is aestheticallypleasing to the viewer and does not provide a background detracting fromthe information content of the image. Particularly desirable reflectingagents will be those providing a white background, for viewing thetransfer image, and specifically those conventionally employed toprovide background for reflection photographic prints and, especially,those agents possessing the optical properties desired for reflection ofincident radiation.

An examples of reflecting agents, mention may be made of barium sulfate,zinc sulfide, titanium dioxide, barium stearate, silver flake,silicates, alumina, zirconium oxide, zirconium acetyl acetate, sodiumzirconium sulfate, kaolin, mica, and the like.

Illustrative of the photographic use of the indicator dyes of thepresent invention as optical fllter agents, a photographic film unit maybe prepared by coating, in succession, on a gelatin subbed, 4 mil.opaque polyethylene terephthalate film base, the following layers:

l. a layer of the cyan dye developer1,4-bis-(B-[hydroquinonyl-a-methyl]-ethylamino)-5,8-dihydroxyanthraquinonedispersed in gelatin and coated at a coverage of about 80 mgs./ft. ofdye and about I mgs./ft. of gelatin;

20 hydroquinonylethyl]-phenylazo)-4-isopropoxy-l-naphthol dispersed ingelatiin and coated at a coverage of 70 mgs./ft. of dye and about 120mgs./ft. of gelatin;

5. a green-sensitive gelatino-silver iodobromide emulsion coated at acoverage of about 120 mgs./ft. of silver and 60 mgs./ft. of gelatin;

6. a layer comprising the acrylic latex sold by Rohm and Haas Co. underthe trade designation B-l5 and polyacrylamide coated at a coverage ofabout 100 mgs./ft. of B-l5 and about mgs./ft. of polyacrylamide;

7. a layer of the yellow dye developer 4-(p-[B-hydroquinonylethyl]-phenylazo)-3-(N-n-hexyl-carboxamido)-l-phenyl-S-pyrazoloneand the auxiliary developer 4'-methylphenyl hydroquinone dispersed ingelatin and coated at a coverage of about 50 mgs./ft. of dye, aboutmgs./ft. of auxiliary developer and 50 mgs./ft. of gelatin;

8. a blue-sensitive gelataino-silver iodobromide emulsion coated at acoverage of about 75 mgs./ft. of silver and about 75 mgs./ft. ofgelatin; and

9. a layer of gelatin coated at a coverage of about 50 mgs./ft. ofgelatin.

Then a transparent 4 mil. polyethylene terephthalate film base may becoated, in succession, with the following illustrative layers:

1. a 7:3 mixture, by weight, of polyethylene/maleic acid copolymer andpolyvinyl alcohol at a coverage of about 1400 mgs./ft. to provide apolymeric acid layer;

2. a graft copolymer of acrylamide and diacetone acrylamide on apolyvinyl alcohol backbone in a molar ratio of l:3.2:l at a coverage ofabout 800 mgs./ft.", to provide a polymeric spacer layer; and

3. a 2:1 mixture, by weight, of polyvinyl alcohol andpoly-4-vinylpyridine, at a coverage of about 900 mgs./ft. and includingabout mgs./ft. phenyl mercapto tetrazole, to provide a polymericimage-receiving layer.

The two components thus prepared may then be taped together in laminateform, at their respective edges, by means of a pressure-sensitivebinding tape extending around, in contact with, and over the edges ofthe resultant laminate.

A rupturable container comprising an outer layer of lead foil and aninner liner or layer of polyvinyl chlo- 2' a red sensitive gelatinosilver iodobromide emul ride retaining an aqueous alkaline processingsolution sion coated at a coverage of about 225 mgs./ft. ofsilcomprising: ver and about mgs./ft. of gelatin; Water I00 cc.

50 Potassium hydroxide ll.2 gms. 3. a layer of the acrylic latex sold byRohm and Haas Hyd xyethy] cellulose (high Co., Philadelphia,Pennsylvania, U.S.A., under the viscosity) [co y avallablq from HerculesPowder Co., Wilmington, trade designation AC-6l and polyacrylamidecoated at Delaware, under the "ads name a coverage of about 150 mgs./ft.of AC-61 and about, Nalrasol 8"- 2 N-phenethyl-a-picohmum bromide 2.7gms. 5 mgs[ft. of polyacrylamide, Benzmriazole 1.15 gms. 4. a layer ofthe magenta dye developer Z-(p-[B- Titanium dioxide 5 g 2 .0 gins.

H H N CH N nC H O CH -CO may then be fixedly mounted on the leading edgeof each of the laminates, by pressure-sensitive tapes interconnectingthe respective containers and laminates, such that, upon application ofcompressive pressure to a container, its contents may be distributed,upon rupture of the containers marginal seal, between the poly mericimage-receiving layer and next adjacent gelatin layer.

The photosensitive composite film units may be exposed through stepwedges to selectively filter radiation incident on the transparentpolyethylene terephthalate layer and processed by passage of the exposedfilm processing, the multicolor dye transfer image formation may beviewed through the transparent polyethylene terephthalate layer againstthe titanium dioxide background provided by distribution of the pigmentcontaining processing composition between the polymeric image-receivinglayer and gelatin layer 9 of the photosensitive component. The film unitmay be exposed to incident light and the formation of the image may beviewed upon distribution of the processing composition by reason of theprotection against incident radiation afforded the photosensitive silverhalide emulsion layers by the optical filter agents and by reason of theeffective reflective background afforded by the titanium dioxide.

The spectral absorption characteristics of the indicator dye prepared inExample 1 above are graphically illustrated in FIG. 13 of theaforementioned copending application Ser. No. 103,392 which graphrepresents the optical transmission density, i.e., absorbance of the dyemeasured on a logarithm scale over the wavelength range of 350 nm. to750 nm. in aqueous alkaline solution at a pH substantially above itspKa.

The film unit detailed above is similar to that shown CO-CH n N c u inFIG. 2 and related FIGS, 3-4 of aforementioned copending U.S. Patentapplication Ser. No. 101,968. The negative component of the film unitincluding the photosensitive strata and associated dye-image-formingmaterial; the positive component including the timing, neutralizing anddyeable layers; and the processing composition including its components,such as, the alkaline material and various addenda are described indetail in application Ser. No. 101,968. For convenience, thespecification of this application is specifically incorporated herein.

Besides the above photosensitive element, the dyes of the presentinvention may be employed in composite photosensitive elements, ingeneral, where the dyeable stratum along with any associated layers maybe contained together with the photosensitive strata as a unitary filmunit which may be termed an integral negative-positive film unitcomprising a negative component including the aforementioned essentiallayers and a positive component including at least the dyeable stratumin which the color transfer image is to be formed. The essential layersare preferably contained on a transparent dimensionally stable layer orsupport member positioned closest to the dyeable stratum so that theresulting transfer image is viewable through this transparent layer.Most preferably another dimensionally stable layer which may betransparent or opaque is positioned on the opposed surface of theessential layers so that the aforementioned essential layers aresandwiched or confined between a pair of dimensionally stable layers orsupport members, at least one of which is transparent to permit viewingtherethrough ofa color transfer image obtained as a function ofdevelopment of the exposed film unit in accordance with the known colordiffusion transfer processes. It will be appreciated that all of thesefilm units, like the specific one detailed above, may optionally containother layers performing specific desired functions, e.g.,

spacer layers, pI-I-reducing layers, etc.

Examples of such integral negative-positive film units for preparingcolor transfer images viewable without separation are those describedand claimed in aforementioned U.S. Pat. No. 3,415,644 and in US. Pat.Nos. 3,415,645, 3,415,646, 3,473,925, and 3,573,043,

In general, the film units of the foregoing description, e.g., thosedescribed in the aforementioned patents and/or copending applications,are exposed to form a developable image and thereafter developed byapplying the appropriate processing composition to develop exposedsilver halide and to form, as a function of development, an imagewisedistribution of diffusible dye image-providing material which istransferred, at least in part by diffusion, to the dyeable stratum toimpart thereto the desired color transfer image, e.g., a positive colortransfer image. Common to all of these systems is the provision of areflecting layer between the dyeable stratum and the photosensitivestrata to mask effectively the latter and to provide a background forviewing the color image contained in the dyeable stratum, whereby thisimage is viewable without separation, from the other layers or elementsof the film unit. As discussed previously, in some embodiments thisreflecting layer is provided prior to photoexposure, e.g., as apreformed layer included in the essential layers of the laminarstructure comprising the film unit, and in others it is provided at sometime thereafter, e.g., by including a suitable light-reflecting agent,for example, a white pigment, such as, titanium dioxide, in theprocessing composition. As an example of such a .preformed layer,mention may be made of that disclosed in the copending applications ofEdwin H. Land, Serial Nos. 846,441, filed July 31, 1969, and 3,645,filed Jan. 19, 1970, now US. Pat. Nos. 3,615,421 and 3,620,724. Thereflecting pigment may be generated in situ as is disclosed in thecopending applications of Edwin H. Land, Serial Nos. 43,741 and 43,742,both filed June 5, 1970, now US. Pat. Nos. 3,647,434 and 3,647,435. In aparticularly preferred form, such film units are employed in conjunctionwith a rupturable container, such as, that used above, containing theprocessing composition having the light-reflecting agent incorporatedtherein which container is adapted upon application of pressure ofdistributing its contents to develop the exposed film unit and toprovide the light-reflecting layer.

As noted previously, the photographic use of the dyes of the presentinvention as optical filter agents to prevent post-exposure fogging of aselectively exposed photosensitive material is not limited to diffusiontrans fer processes nor to such processes employing compositephotosensitive elements. While the use of such dyes in compositemulticolor diffusion transfer film units is a particularly preferredembodiment of the present invention, these dyes may be used with equallyeffective results in any photographic process where it is desired toprotect a photosensitive material from incident radiation actinic to thephotosensitive material within the wavelength range capable of beingabsorbed by the dye. For example, the subject dyes may be used inconventional tray photographic processing as a component of theprocessing bath, or they may be present in a layer coextensive with oneor both surfaces ofa layer of pho-' tosensitive material to be processedusing conventinal tray procedures, provided that they arenon-lightabsorbing prior to photoexposure and also subsequent todeveloping the latent image unless the layer containing the dye is to beremoved subsequent to processing.

In such procedures, the photo-exposed photosensitive material will, ofcourse, be transferred from the camera to the processing bath in theabsence of radiation actinic to the material,

The subject dyes also may be employed in diffusion transfer processeswhere the photosensitive and imagereceiving elements are separatedsubsequent to the formation of a transfer image or where a spreadersheet is separated from the photosensitive element to reveal a finalimage in the negative. In addition to the composite diffusion transferstructures described above, the subject dyes may be used with compositediffusion transfer film units where the final image is to be viewed bytransmitted light. Also they may be used in composite film unitsspecifically adapted, for example, for forming a silver transfer image,for developing a negative silver image by monobath processing, forobtaining an additive color image, and for obtaining a dye image by thesilver dye bleach process which structures are described in detail inaforementioned copending US. application Ser. No. 101,968, particularlywith reference to FIGS. 10 to 13 of the applications drawings.

Although the invention has been discussed in detail throughout employingdye developers, the preferred image-providing materials, it will bereadily recognized that other, less preferred, image-providing materialsmay be substituted in replacement of the preferred dye developers in thepractice of the invention. For example, there may be employed dyeimage-forming materials such as those disclosed in US. Pat. Nos.2,647,049; 2,661,293; 2,698,244; 2,698,798; 2,802,735; 3,148,062;3,227,550; 3,227,551; 3,227,552; 3,227,554; 3,243,294; 3,330,655;3,347,671; 3,352,672; 3,364,022; 3,443,939; 3,443,940;

3,443,941; 3,443,943; etc., wherein color diffusion transfer processesare described which employ color coupling techniques comprising, atleast in part, reacting one or more color developing agents and one ormore color formers or couplers to provide a dye transfer image to asuperposed image-receiving layer and those disclosed in US. Pat. No.2,774,668 and 3,087,817, wherein color diffusion transfer processes aredescribed which employ the imagewise differential transfer of completedyes by the mechanisms therein described to provide a transfer dye imageto a contiguous image-receiving layer, and thus including the employmentof image-providing materials in whole or in part initially insoluble ornondiffusible as disposed in the film unit which diffuse duringprocessing as a direct or indirect function of exposure.

In view of the foregoing, it will bereadily apparent that the subjectdyes are useful generally in photographic processes for producingsilver, monochromatic and multi-color images using any photosensitivematerial including conventional and direct positive silver halideemulsions. Depending upon the selected photosensitive material, one ormore of the dyes may be used alone or in combination with anotheroptical filter agent, such as another light-absorbing dye, which seconddye may be non-color-changing or another pH sensitive dye. If theselected dye or dyes do not possess the desired stability in theprocessing composition for long term storage therein, they may beinitially disposed in the film structure or stored in adouble-compartmented pod or in one of two associated pods separate fromthe processing solution until such time as the pod(s) are rupturedwhereupon the dyes are admixed with the processing solution.

since certain Changes may be made in the above wherein R is selectedfrom hydrogen and sulfo, R is seproduct and process without departingfrom the scope lected from hydrogen and alkyl havmg 1 to 20 Carbon ofthe invention herein involved, it is intended that all atoms and Xrepresents the atoms necessary to matter contained in the abovedescription shall be in- 5 Plete a ring-closing moiety Selected fromPhthalide, terpreted as illustrative and not in a limiting sense.carboxy substituted p h li and p h li What is claimed is: 2. Anindicator dye as defined in claim 1 wherein said 1. An indicator dyehaving the formula: dye is a phthalide.

3. Di-(5-hydroxy-4-azaphenanthren-8-yl)77carb0xyphthalide 4.Di-(6-sulfo-5-hydroxy-4-azaphenanthren-8-yl)7- carboxyphthalide.

1. AN INDICATOR DYE HAVING THE FORMULA:
 2. An indicator dye as definedin claim 1 wherein said dye is a phthalide. 3.Di-(5-hydroxy-4-azaphenanthren-8-yl)77carboxyphthalide 4.Di-(6-sulfo-5-hydroxy-4-azaphenanthren-8-yl)7-carboxyphthalide.